Carburetor



May 21, 1940. l E Q wlRTH 2,201,603

cARBuREToR Filed may 1, 1957 Il i.; I 4o /4 'FIGJ 5g@ l ze 58 54 o 20 34 f :S i

L /C I 26 L K r z- 30 5 ,la w i INVEN TOR Emu. O :Wurm

Patented May 21, 1940 UNITED STATES n cAnBUnE'ron Emil o. Wirth, south nena, Ind'., assignor to Bendix Products Corporation, Ind., a. corporation of Indiana.

South Bend,

Application MayA 1, 193i, serial No. 140,075 Y 8 Claims.

containing an appreciable percentage of low boiling point constituents andinterferes with proper metering of thefuel, thereby making it extremely difficult to maintain a proper fuel-air mixture. 15 One of the objects of the present invention is to provide a carburetor in which fuel is metered accurately without interference, due to-boiling. Preferably the fuel is fed to the nozzle from the lower part of a fuel chamber and a current of 20 air is passed across the surface of the fuel in the chamber to remove the more volatile constituents, the current of air being then conducted into the carburetor mixture conduit adjacent the inlet end thereof. 25 Other objects, advantages and novel features of the invention will be apparent from the following description when read in connection with the accompanying drawing, in which:

^ Figure 1 is a central section with parts in ele- 30 vaion of a carburetor embodying the invention;

Figure 2 is a similar partial view of a modified construction.

The illustrated carburetor comprises a conduit 35 or induction passage I0 constricted at l2 to form a venturi and having a chokevalve I4 and a. throttle valve I6. A fuel chamber is formed around the central portion of the conduit I and preferably includes a body portion I8 formed 4o integral with the lower part of the conduit and afcover 20 formed integral with the upper part of the conduit. 'Ihe cover 20 and body I8 aswell as the two parts of the conduit I0 are connected in a -horizontal plane adjacent the upper part of the fuel chamber and above the normal fuel level therein with a gasket 22 between them. Suitable means are provided to maintain the level of fuel in the fuel chamber substantially constant, such means as shown comprising a. oat 24 operating a valve 26which controls inlet of fuel into the fuel chamber from a pipe 28. The pipe 28 may connect to a fuel pump, a tank or any other suitable source of supply.

Fuel from the fuel chamber is supplied to the 55 conduit I0 through a nozzle 30 opening into the (ci. 2in-7.2)

lower pa-rt of the fuel chamber through a metering orice 32 and discharging into a primary venturi 34 arranged centrally of the venturi l2. The central portion of the nozzle 30 'is formed with a seriesl of 'bleed openings communicating with a chamber 3B which is connected to the inlet end of the conduit I0 by a tube 38. Thus air is bled into fuel passing through the nozzle and a mixture of fuel and air is. discharged into the venturi 34 to be mixed with air flowing therelw through.

Air is supplied to the upper end of the conduit I0 through an air, cleaner indicatedA generally at 40. The illustrated air cleaner is of a known commercial type including a body of oil or the like 42 over which the air sweeps and a filter mass 44 for removing from the air any foreign particles carried thereby. 'I'he cleaned air passes from the lter mass downwardly through a central discharge tube 46 into the upper end of the conduit 2O I0. It will be understood that the carburetor is not restricted to use with the particular air cleaner illustrated but that any other suitable type of cleaner could be employed or that the carburetor could be used without any air cleaner.

With a carburetor as so far described it has been found that diillculty may be encountered in properly metering the fuel due to boiling of the fuel in the float chamber and nozzle, this diifv culty being particularly pronounced when the carburetor is mounted closely adjacent a hot part of the engine and when so-called Winter gasoline containing a high percentage of volatile constituents is used. This diilculty isovercome according to the present invention by removing most of the highly volatile constituents prior to metering of the fuel through the orifice 32 and prior to entryy of the fuel-into the nozzle so that correct proportions of fuel and air are maintained at alltimes. The volatile constituents are preferably drawn off through openings 48 in the gasket 22 and through a passage 50 into the inlet end of the conduit I0 where they are mixed with airand led into the engine. The openings 48 are staggered with respect to the passage 50 to 45 prevent fuel from splashing up into the passage and being drawn into the conduit Ill. A short tube 52 is connected to the passage 50 and projects into the conduit l0 and opens generally in the direction of incoming air to be subject to the impact effect thereof. lThis reduces the suction effect on the passage 50, due to the restricting or choking effect of the air cleaner, which suction tends to become too high at high air flows, and, the arrangement thus tends to maintain a sub- 55 stantially constant suction on the passage 50 at all times. The tube 52 also projects out toward the center of the air stream which may be somewhat constricted by the tube 46 of the air cleaner so that the impact thereon is representative of the true air flow condition. Tube 52 opens` into the induction passage anterior to the choke valve I4, since otherwise closing of the choke valve would put the fuel chamber under a suction equal to that exerted on the nozzle 30 when the choke valve is closed, so that no enrichment of the mixture would ble/accomplished.

Passage 50 is provided with a restricted opening 53 to the atmosphere, which reduces the effective suction transmitted from tube 52 to the fuel chamber and also tends to prevent any liquid fuel which may be drawn into the lower end of passage from `being drawn upwardly into the induction passage. v

In order to reduce the suction in the fuel chamber (caused by the resistance of the vair cleaner to the ow of air therethrough) and to provide a current of air to sweep away the volatilized constituents, an air inlet is provided at the opposite side of the fuel chamber from the passage 5|). The air inlet may be formed by a short tube 54 secured to the cover 20 and opening into the fuel chamber through a hole or series of holes 5B in the gasket 22. preferably offset to prevent fuel from splashing out the tube and a cap 58 may be provided to keep dirt away from the inlet end of the tube.

The air inlet opening provided by the tube 54 is preferably so proportioned withrespect to the passage 50 that a pressure drop of approximately 3/8 inch of water will exist between the tube and passage during the time the engine is in operation. This means that the fuel chamber will be subjected to a substantially constant suction which 4will assist in vapqrizing the more volatile constituents of the fuel but which is not enough to cause vaporization of those constituents which will flow through the orifice 32 andthe nozzle without boiling..

In order to conduct away from the engine any vaporized fuel which boils out the fuel chamber ater the engine is stopped to prevent .ooding of the engine or danger of fire, the upper end of tube 54 is disposed at a lower level than that of thetube 52, and in addition tubeA 54 may, if desired, be provided with a drain pipe 60 leading downwardly to a point remote from the engine. Since the vapor is heavier than air it will flow through the pipe 60 to such remote point whereY it cannot interfere with engine operation nor create a possibility of fire or explosion when the engine is restarted.

When an air cleaner is used it creates a variable resistance to the flow of air into the carburetor due to the fact that its filter mass may be dry at one time and Wet at another. 'I'his causes a variable choking eiect on the carburetor tending to increase the richnessof the mixture but since the passage 50 is responsive to suc- -tion at the. air cleaner outlet any choking'effect produced by the `air cleaner is reflected in increased suction in the fuel chamber which tends to decrease the richness of the mixture. r By properly proportioning the effective cross sec tions of passage 50, tube 54, and opening 53, these two effects can be made substantially to cancel each other so that the richness of the mixture is notresponsive to variations of flow resistance in the airvcle'aner.

Figure 2 illustrates a modified construction,

The holes 56 and tube 54 are parts therein corresponding to like parts in Figure 1 being designated by the same reference numerals plus |00. In this construction the tube |54 extends into the conduit and opens in the direction of incoming air, the choke valve ||4 being provided with a slot ||5 through which the tube |54 extends when the valve is closed. The tube |52 is reversed from the position shown in Figure 1 and opens in the direction of' air flow so that it is not subject to impact of the incoming air. The pipe |50 is connected to the tube |54 below the level of the tube |52 to,

conduct away vapor when the engine is stopped and is of relatively small diameter so that it will not interfere with the balance between tubes |52 and |54.

In the usual automobile construction the engine is located in front under a hood, into which air flows through the radiator, and at high speeds the impact of this air flow raises the pressure under the hood as much as two inches of water above atmospheric. The herein disclosed system of drawing vapor from under the hood through the float chamber and thence into the mixture conduit may be employed and be so proportioned to maintain the float chamber at atmospheric pressure or slightly subatmospheric pressure so that a substantially uniform pressure is maintained in the float chamber over the wide range of vehicle speeds, and particularly at high speeds during which the pressure under the hood would ordinarily tend to enrich the mixture by the increased pressure in the float chamber. r

Due to the difference in pressure on the tubes |52 and |54 created by the air flow, air

will be circulated through the tube |54, across.

drop between the two tubes can be controlled p by proportioning the tube sizes and the angles of their opening to maintain substantially any desired amount of suction in the fuel chamber. Also any fluctuations in suction due to varying resistance in the air cleaner will be communicated to the fuel chamber through both tubes |52 and |54 and will compensate for the choking effect of the air cleaner.

While two embodiments of the invention have been shown and described, it will be apparent that many changes mightbe made therein and it is not intended to limit the scope of the invention to the forms shown nor otherwise than by the terms of the appended claims.

What is claimed is:

1. A carburetor comprising an induction passage, a choke valve in the inlet end of the induction passage, a fuel chamber, a fuel nozzle connected to said fuel chamber and discharging into the .induction passage posterior to the choke valve,

induction passage, a fuel chamber, a nozzle con-y nected to the fuel chamber and discharging into the induction passage, a pair of conduits leading from substantially spaced points in the top of the fuel chamber to the induction pas? sage anterior to the choke valve, one. of said conduits opening in one direction and the `other opening in the other direction, and a pipe con- |52y back to the conduit. The ypressure nected to oneof said conduits below the point at which they communicate with the induction passage to conduct away heavier-than-air fuel vapor.

.3. In a plain tube carburetor comprising a downdraft induction passage adapted to receive an air cleaner at the entrance thereof, a choke valve in the induction passage, a constant level fuel chamber ysupplying fuel to the induction passage posterior to said valve, a conduit leading from the fuel chamber above the fuel level thereof and opening into the induction passage anterior to the choke valve when said` valve is in a closd position, a vent tube having an atmospheric inlet and having an outlet in the fuel chamber above the fuel level thereof and at a point substantially spaced from the inlet to said conduit, said conduit including a tube projecting into the induction passage and opening up! wardly toward the induction passage inlet to thereby be subjected to but a moderate depression during periods of operation for creating a draft of aix` across the surface of the fuel in the fuel chamber, and a baille disposed above the fuel level of said fuel chamber to prevent liquid fuel from entering the conduit and tube.

4. In a plain tube carburetor comprising an induction passage, a choke valve therein, a constant level fuel chamber supplying fuel vto the induction passage, a conduit having an inlet at one side `of the fuel chamber above the fuel level thereof and having an upwardly opening outlet in the induction passage anterior to the choke valve when in closed position, a vent tube leading from a source of substantially atmospheric pressure to the other side of the fuel chamber above thefuel level thereof, means for creating a. depression at the outlet of saidconduit to thereby induce a moderate draft of air across the surface of the fuel in the fuel chamber, and a discharge tube leading from thevent tube to a point remote from the carburetor to conduct away heavier-than-air fuel vapor when the carburetor is not in operation. L

Y5. A carburetor comprising a downdraft induction passage, a choke valve therein, a fuel chamber, a nozzle connected to the fuel chamber and discharging into the induction passage, a conduit having an inlet in the top of the fuel chamber at one side thereof and having an upwardly opening outlet in the induction passage anterior to the choke valve, a vent tube having an air inlet and having an outlet in the top of the fuel chamber at the opposite side thereof, and means for creating a depression on said conduit outlet during operating periods to draw fuel vapors into the induction passage from above the surface of the fuel in the fuel chamber and to create a draft of air across said surface to thereby permit additional-fuel to vaporize.

6. A carburetor comprising a downdraft in' duction passage, a choke valve therein, a fuel and opening into the upper end of the induc' tion passage anterior 'to the choke valve when closed, said vapor conduit including a tube projecting into theinduction passage and opening upwardly toward the induction passage inlet,

means creating a depression at the outlet of said tube during periods of, operation to therebydraw fuel vapors intol the induction passage from above the surface of the fuel in the fuel chamber and to create a draft of air across said surface to permit additional fuel to vaporize, and an atmospheric vent in said vapor conduit to partially satisfy the depression therein.

7. A carburetor comprising a downdraft induction passage, a choke valve therein, a fuel cham- ,ber below the upper end of the induction passage, a fuel nozzle connected to the fuel chamber and discharging into the inductionv passage, a vent tube having an` air inlet and leading into the top of the fuel chamber at one side thereof, a conduit leading from the top of the fuel chamber at the opposite side thereof and having an outlet in the upper end of the induction passage anterior to the choke valve, means for creating a lower pressure at said conduit outlet than at said air inlet during periods of operation to thereby cre-1 ate'a draft of air across the surface of the fuel in the fuel chamber, and a pipe connected to the vent tube at an elevation lower than either the conduit outlet or the air inlet and leading to a point remote from the carburetor.

8. A carburetor comprising a downdraft induction passage, a choke valve therein, a fuel chamber formed with a lower body portion and a cover adapted to be connected in a substantially horizontal plane above the normal fuel level, a nozzle connected to said fuel chamber and discharging .into the induction passage, said cover being formed with an air vent opening, a vapor conduit leading from said cover at a point substantially spaced from said air vent opening and having an o utlet in the induction passage anterior to said choke valve, means creating a depression in the induction passage anterior to the choke valve during operation to thereby induce a flow of air and fuel vapor from said outlet, and a gasket between the body portion and cover. formed with openings to establish communication be- .tween the body 'portion and the ventA and vapor conduit, said openings being so arranged as to form a tortuous passage throughthe fuel chamber from the vent to the vapor conduit thereby to prevent fuel from splashing out the vent or the vapor conduit.

EMIL 0. WIRTH. 

